1. Field of the Invention
The present invention relates to a video-on-demand (VOD) system, and more particularly to a user oriented VOD system which enables a user to resume viewing of a specific video program after an interruption.
2. Background of the Related Art
Generally, a video-on-demand service stores programs such as movies, sports and educational programs in a main computer to allow a user to freely select and view a program at any time period. Particularly, the VOD service provides multimedia data including text, audio and video data. For example, character data is transmitted with a transmission speed of 28.8 Kbps, audio data is transmitted with a transmission speed of 64 Kbps based on telephone lines, and video data is transmitted with a transmission speed of 1.5 Mbps based on MPEG-1 standard. Thus, the VOD service enables a user to view a program selected according to the individual taste, regardless of the time, as well as allow users to play, rewind, pause and record the program as in a video cassette recorder (VCR) FIG. 1A is a block diagram of a general VOD system.
Referring to FIG. 1A, a video server 22 provides general VCR functions such as play, rewind, and fast forward, when requested by users. The video server 22 can be implemented by developing a dedicated hardware for extracting video streams from a hard disk drive, independent from the performance of a central processing unit (CPU). A multimedia database 21 allows the storage and access to extensive multimedia data of various sizes such as text, image, animation, audio, and video. Also, the database 21 includes data to support a search of a particular data. Thus, the database 21 has an index structure and search algorithm for searching the media.
An asynchronous transfer mode (ATM) exchange or switch 23 connects the video server 22 to a subscriber loop through the digital transmitting unit 24. The digital transmitting unit 24 may be an asymmetric digital subscriber line (ADSL) type using the existing telephone lines, a hybrid network type using a coaxial cable and optical fiber, or an ADSL type capable of transmitting compressed information using the existing 2-line subscriber lines. Because a service can be provided using the existing telephone lines, an ADSL digital transmitting unit 24 is more advantageous.
A set-top box (STB) 100 is a repeater which restores the original digital video signal from a compressed digital video signal transmitted from the server. The STB 100 also converts the restored digital video signal into an analog video signal and transfers the analog video signal to a subscriber device. Thereafter, the STB 100 processes a signal from a subscriber through an input device such as a remote control and performs a network connection function.
To provide the VOD service as described above, a communication network of a high-speed and a large-capacity optical fiber are necessary. However, in regions or countries where a foundation has not been built, a video-dial-tone (VDT) service, as shown in FIG. 1B, using telephone lines has been established as a phase prior to a complete VOD service. The VOD service may also be provided under the existing local area network (LAN) environment.
Generally, when a user wishes to a certain program, the user can view the program by connecting to the VOD system and selecting the program. If the user cannot view the whole program at one time, the VOD allows the user to view the program in multiple sittings. For example, U.S. Pat. No. 5,818,439 discloses a VOD system including a video server that manages users as subscribers and stores a position at which a user stops viewing a program. Thereafter, if the same user requests viewing of the same program, the video server displays the program from the position at which the viewing of the program has been interrupted. At this time, the VOD system may also display the contents of the previously viewed portion of the program by a summary using still images.
Therefore, according to the VOD system in the related art, when the user resumes viewing of a program after an interruption, the user must connect to the same video server that previously provided the VOD service, because only the same video server stores the position at which the viewing was stopped. However, if the same video server is being used by another subscriber, the video server cannot provide the interrupted program to the user until there are enough resources. In such case, the user may use a different server to view another program or the interrupted program by manually forwarding to the position at which the viewing was stopped. This causes the user inconvenience.
Also, when many users stops viewing programs in the middle of the program, the corresponding server must continuously maintain and manage the position information of the interrupted programs, regardless of whether the users will resume viewing the interrupting program. Thus, the load of the video servers increase while the maintenance and management of the whole system become more complicated. Moreover, because the system provides users with contents of the previous viewing based on still images, when a user resumes viewing an interrupted program, the contents may not be clearly comprehensive.